Watch List notes:

Potosi, Bolivia, cob 4 reales, Philip III, assayer M, NGC shipwreck effect / Sao Jose.S-P18; KM-9; Cal-771.Full shield, most of cross (bold) despite light surface corrosion, full mintmark P, toned in crevices.With original (generic) certificate from the salvors.Recovered from:

Estimate: 125-200 USD